Transcript t 0 - UNAVCO

Current Land Subsidence in the Houston
Metropolitan Area, Texas, Derived from
GPS Observations (1993-2012)
Guoquan (Bob) Wang
University of Houston
With contributions from graduate students: Timothy J. Kearns, Jiangbo Yu, Linqiang
Yang, Xueyi Jia, and Jianjun Jiang
Outline
• GPS Geodesy Infrastructure in the Houston area
Public available GPS stations (Hardware)
Stable Houston Reference Frame (SHRF) (Firmware)
Single-receiver phase ambiguity resolved GIPSY PPP resolution (software)
• Current subsidence mapping (2005-2012)
• Scientific Questions:
(1) Is there deep seated (or fault-controlled) subsidence in the Houston area?
(2) When will the current subsidence stop?
3 m within 30 years, 10 cm/year
(USGS, Coplin and Galloway,
2009)
(USGS, Kasmarek et al., 2009)
6m
Historic Subsidence in Houston
USGS
Houston Ship Channel Area
Geodesy Infrastructure: Permanent GPS Stations
Harris-Galveston Subsidence District (70+)
Texas Department of Transportation 15+
83 GPS +11 Extensometers
City of Houston, others
HoustonNet
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NSF MRI: 40 GPS; UH: 10 GPS
Subsidence, faulting, and salt dome uplift
Hurricane intensity forecasting
Civil engineering community---buildings, bridges, dams, sea walls
Geodesy Infrastructure: The Stable Houston Reference Frame
Helmert Transformation
7 years: 2005-2012
Wang et al., 2013
14-Parameter Similarity Transformation
(1) Translation along the respective axis (in meters)
(2) Differential Scaling of the respective axis (ppb)
(3) Counterclockwise Rotations (in radians)
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14-Transformation Parameters
Transformation Parameter
Unit
Tx(t0)
Ty(t0)
Tz(t0)
Rx(t0)
Ry(t0)
Rz(t0)
s(t0)
dTx
dTy
dTz
dRx
dRy
dRz
ds
cm
cm
cm
mas
mas
mas
ppb
cm/year
cm/year
cm/year
mas/year
mas/year
mas/year
ppb/year
*Pearson and Snay (2013), Table 7
IGS08 to SHRF
t0 = 2012
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
-1.07250
-1.05876
-3.54574
1.15720
-0.93885
-0.33224
1.37220
IGS08 to NAD83(2011)
t0 = 1997*
99.34300
-190.33100 NGS
-52.65500
25.91467
9.42645
11.59935
1.71504
0.07900
-0.06000
-0.13400
0.06667
-0.75744
-0.05133
-0.10201
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No-linear
subsidence rate
18 Years
Jersey Village
Spatial and temporal
variation of subsidence
Ground Deformation at Closely-Spaced (4 km) GPS Sites
Recent Subsidence Mapping (2005-2012)
85 years
6m
83 GPS +11 Extensometers
Maximum subsidence rate <=2.5 cm/year
< 5 mm/year
7 years: 2005-2012
Aquifer Profile: Chicot + Evangeline
USGS
3600 ft
Question 1: Is there deep-seated (fault-controlled) subsidence in
the Houston-Galveston area?
Gulf Coast Geology and faults
Subsidence vs. Faulting
Subsidence---pumping (??%)+ faulting (??%)
Ortega, 2013
USGS Borehole Extensometers
Compaction meter
USGS
13 extensometers at 11 sites
40 years: 1974—2013
Addicks Borehole Extensometer (-549 m)
Co-Located GPS and Extensometer Monitoring Site (ADKS)
+15 years
Wang et al., 2014
18 years
40 years
Drought of 2011
Drought of 2005
Wang et al., 2014
Journal of Surveying Engineering
Conclusion: The compaction
measurements from the long-term
extensometers are reliable and the
accuracy is about a few millimeters.
Co-located GPS and Extensometer Sites
ADKS(-549 m)
NETP (-591 m)
LKHU (-661 m)
22 years
Conclusion: Compacted aquifers are limited to above -600 m
Clear Lake—Jonson Space Center Sites
Clear lake Deep Borehole (-936 m)
50m
Clear lake Shallow Borehole (-530 m)
Jonson Space Center(-235 m)
2.5 km
37 years
Conclusion: No compaction below -530 m
-530 m
USGS, 2009
Conclusion: Only partial of the Evangeline aquifer had been compacted!
Coastal Subsidence: Galveston vs. New Orleans
4 mm/year
It appears no considerable tectonic subsidence occurs currently in the HoustonGalveston area.
UH Coastal Center “Vertical” GPS Array
-10 ft
-20 ft
-30 ft
Borehole GPS
-1 ft
Question 2: When will the subsidence cease?
1978-1998
38 years
Conclusion: It took 20 years (1978-1998) to halt the subsidence in the southeast part.
38 years
Conclusion: 2005+20=2025
Summary
•
The ground water and aquifer systems respond slowly to human actions. It
took almost two decades (1980s and 1990s) to halt the subsidence in the
south-east part of the Houston metropolitan area. Therefore, a long-term
perspective is needed to manage groundwater resources and control land
subsidence.
• The spatial and temporal variation of subsidence could be very considerable!
subsidence=f(x,y,z t)
• The groundwater regulations implemented by the HGSD are very successful
in reducing subsidence rate in the Houston area. Currently, there is no
considerable deep-seated or fault-controlled subsidence in the HoustonGalveston area. Current aquifer compaction is limited to about -530m.
Thank you!
Stable: v=0